Auditory agnosia. Analysis of a case with bilateral subcortical lesions

We report a case of typical auditory agnosia. It is unique in that the clinical picture began with generalized auditory agnosia for verbal and nonverbal sounds and changed, over a period of two months, to a restricted auditory agnosia, confined to the recognition of nonverbal sounds. The lesions, confirmed by CT scanning and MRI, were subcortical bilaterally, without evidence of cortical damage, and have not previously been described. The results of audiological studies on temporal discrimination were similar to those described for bilateral temporal lobe lesions. The relationships between click intervals and the threshold to detect sound, and between numbers of clicks and the threshold, were also examined. We observed a tendency for the threshold to decline as the number of clicks was increased or the interval between two clicks was shortened. These phenomena are similar to temporal summation in cellular neurophysiology and we speculate that this phenomenon is an important factor in the auditory disturbances shown by the present case.